Electrical frequency stabilizer or time control device



ELECTRICAL FREQUENCY STABILIZER 0R TIME CONTROL DEVICE Filed June 1-,lea

INVENTOR JOHN mum; sMALE E/L L a (aim ATT RNEY' Patented Aug. 18, 1931UNITED STATES PATENT oFHcE JOHN ARTHUR SMALE, F BRENTWOOD, ENGLAND,ASSIGNOR TO RADIO CORPORATION OF AMERICA, A. CORPORATION OF DELAWAREELECTRICAL FREQUENCY STABILIZER 0R TIME CONTROL DEVICE Application filedJune 1, 1928, Serial No. 282,222, and in Great Britain June 27, 1927.

This invention relates to electrical frequency stabilizers or timecontrol devices.

- lt is found that with time period devices such as tuning forks, thereis a liability for slow and small changes of frequency to ocour and, thepresent invention has for its principal object to provide means wherebysuch changes may be corrected automatically under the control of amaster time device,

such as a chronometer.

According to the present invention a frequency stabilizer or timecontrol device comprises in combination a time period device. such as atuning fork, means, such as a damping coil, for increasing or decreasingthe frequency of said time period device, a master time device, such asa ehronometer, and means for controlling the damping'coil or itsequivalent in accordance with the length of time during which agiven'operation of the master time device coincides with a givenoperation of the time period device, so that the fret uency of thelatter device may remain at a su stantially fixed relation to the fre- 5quency of the master time device.

The invention is illustrated in the accom-' panying drawing in which thesingle figure shows schematically one way of carrying out the invention.

Referring to the figure the time period device is a tuning fork 1adapted to be maintained in vibration in the well known way, by means ofa coil 2 energized by a local battery 3 in series with a resistance 4and a contact 5 upon one prong 39 of the fork 1.

The fork is further provided with a second contact 6, preferablyadjustable as to period of contact. The said second contact,"

which may be adapted to be closed when the first mentioned contact isopen, is connected to the grid 7 of a thermionic valve 8, through aseries circuit consisting of a pair of contacts indicated at 9 andadapted to be closed at predetermined intervals (say, every sec- 0nd) bya chronometer 10, a battery 11 (say, 24 volts) whose negative terminalis towards the grid 7, a resistance 12 (say, 4000 ohms), -a'secondbattery 13 (say, 7% volts) whose positive terminal is towards-the grid,and a second resistance 14 (say 2 megohms). The

multaneously for a period of, say 1/80th of negative terminal of thebattery 13 is connected to the cathode 15 of the valve and to a fixedpart of the fork through a condenser 16 of'say, 41 microfarads, shuntedby a leak resistance 17 (say, .25 megohms).

The anode 18 of the thermionic valve 8 is connected to the grid 19 of asecond thermionic valve 20 through a. negative biasing battery 21 of,say, 12 volts, andalso to a common cathode connection through aresistance 22 of, say, 2 megohms, and a high tension battery 23 (say, 50volts) in series, the said resistance and battery being shunted by acondenser 24; of, say, 5 microfarads. The anode 25 of the valve 20 isconnected through a milli-ammeter 26 to a damping coil 27 associatedwith the tuning fork, thence, through a high tension battery 28 (say,120 volts) to the common cathode connection 29. The damping coil is soarranged as to speed up the fork when energized and, if desired, asecond damping coil 30 energized through a variable resistance31 fromthebattery 3 may be provided for purposes of adjustment.

It isto be understood that the numerical values given in the abovedescribed construction are by way of example only, and may be variedwithin wide limits according to requirements.

The operation of the device is as follows- Suppose the correct frequencyof the fork is 35 vibrations per second. Then at each 35th vibration,the contact 6 on the fork and the chronometer contacts 9 will be closedsia second. During this period a negative potential will be applied tothe grid 7 'of the valve 8 from the battery 11 and, when after theexpiration of this period the contacts 9 are opened, the condenser 16slowly discharges through its shunt resistance 17, thereby causing thegrid 7 to return to its normal potential, as determined by. the battery13, and the value of the grid current. It will be seen that the voltagedrop occurring across the resistance 22in the anode circuit of the firstvalve applies a negative potential to the grid 19, and, since thisvoltage drop depends upon the anode current, the impression of negativevoltage upon the grid 7, by l quency thereof.

reducing the anode current, tends to reduce the negative potentialapplied to the grid 19, and the said grid therefore tends to take up thepositive potential determined. by the anode battery 23 associated withthe first is charged to the said potential. By suitably choosing thevalues of the constants of the two grid circuits, the positive andnegative potential excursions of the second grid may be caused to occupya desired period of time (say five seconds) if allowed to persist totheir limits, but, as the contact occurs every second, a mean value ofthe two excursions results and a substantially constant and mean currentdependent upon the second grid potential will flow in the damping coilso long as the duration of coincidence of contact of the fork and theclock remains constant.

If, however, the fork varies its frequency, the duration of contact willbe varied and a correction applied through the damping coil. In thismanner an average control is exerted by the damping coil tending to keepthe average frequency of the fork a constant multiple of the speed ofthe clock or other master time device.

Having now particularly described the nature of my invention, I declarethat what I claim is 1. A frequency stabilizer device comprising incombination a time period device, a master time period device, and meansoperable in accordance with the duration of coincidence between a givenoperation of the time period device and the master time period devicefor increasing or decreasing the frequency of the time period device.

2. A frequency stabilizer comprising a time period device ofsubstantially constant frequency, a master time period device ofabsolute constant frequency, and means operable in accordance with theduration of coincidence between a given operation of the substantiallyconstant time period device and the master time period device forapplying correcting forces to the substantially constant time perioddevice and stabilizing the fre- 3. A frequency stabilizer comprising atime period device of substantially constant frequency, a master timeperiod device of absolute constant frequency, and a thermionic vacuumtube system adapted to become operable in accordance with the durationof coincidence between a given operation of the substantially constanttime period device and the master time period device for applyingcorrecting forces to the substantially constant time period device andstabilizing the frequency thereof.

4. A frequency stabilizer system comprising in combination a mechanicalvibratory system, a damping coil associated therewith, a master timeperiod device, contacts actuated by both said mechanical vibratorysystem and said master time period device, and means for controllingsaid dampingcoil in accordance with the duration of coincidence of theclosure of said mechanical vibrator and said master time period devicecontacts for maintaining the frequency of said mechanical vibratorysystem at a substantially constant multiple of the frequency of closureof the said master time period device contacts.

5. A frequency stabilizer system comprising in combination a mechanicalvibratory system, a damping coil associated therewith, a master timeperiod device, contacts actuated by both said mechanical vibratorysystem and said master time period device, and means for controlling theeffect of said damping coil on said vibratory system in accordance withthe duration of coincidence of the'closure of said mechanical vibratorand said master time period device contacts for maintaining thefrequency of said mechanical vibratory system at a substantiallyconstant multiple of the frequency of closure of the said master timeperiod device contacts.

6. In a system for maintaining substantially constant frequency ofvibratory ele-' ments, a tuning fork, a master time period device andmeans for increasing or decreasing the frequency of the tuning fork inaccordance with the coincidence between the operations of the saidtuning fork andthe master time period device.

7. A system for maintaining substantially constant frequency invibratory elements and the like which includes in combination anelectrically driven tuning fork, a master time period device ofaccurately controlled periodiclty, a vacuum tube associated with saidtuning fork, means for controlling the potentials on the controlelectrode of said vacuum tube in accordance with the periodicity ofvibration of said tuning fork and thereby controlling the currentfiow inthe output circuit'thereof, and means controlled in accordance with thecurrent flow in the output circuit of said vacuum tube for applyingcorrecting forces to said tuning fork in accordance with periodicvariations in the vibration rate of said tuning fork and said constantperiod master time period device.

8.- A system for stabilizing the frequency of vibratory elements and thelike which includes a tuning fork and means for continuously vibratingthe same, a master time period device, contacts associated with bothsaid master time period device and said tuning fork and adapted to beclosed uponthe vibration of said tuning fork, a vacuum tube adapted tohave a negative grid potential thereon controlled in accordance with thecomoval of said potential to said second gridwhen the output current ofsaid first vacuum tube decreases, and means controlled in accordancewith the strength of the output current in the second of said vacuumtubes for applying correcting forces to said tuning fork for increasingor decreasing the frequencv thereof.

9. A system for maintaining substantially constant frequency invibratory elements and .the like which includes in combination anelectrically driven tuning fork, a master time period device ofaccurately controlled periodicity, a vacuum tube system associated withsaid tuning fork and master time period device, means for controllingthe potentials on the control electrodes of said vacuum tube system inaccordance with the periodicity of vibration of said tuning fork andthereby controlling the current flow in the output circuits thereof, andmeans controlled in accordance with the current flow in the outputcircuits of said vacuum tube for applying correcting forces tosaidtuning fork in accordance with periodic deviations in thevibrational rate of said tuning fork from that of said constantfrequency master time period device.

10. A system for stabilizing the frequency of vibratory elements and thelike which includes a tuning fork and means for continuously vibratingthe same, a master time period device, contacts associated with bothsaid master time period device and said tuntarding the removal of saidpotential to said second grid when the output current of said firstvacuum tube decreases, and a damping coil associated with said fork andcontrolled in accordance with the strength of the output current in thesecond of said vacuum tubes for applying correcting forces to saidtuning fork for increasing or decreasing the frequency thereof inaccordance with deviations in frequency of said fork from apredetermined multiple of the frequency of said master time perioddevice.

11. In a system for. stabilizing the frequency of vibratory elements, atuning fork and means for continuously vibrating the same, and aconstant period master control device for checking the constancy ofvibration' of said tuning fork, a set of contacts connected with saidtuning fork and said master control device adapted to be closed uponcoincidence of operation of both of said devices, a vacuum tubeassociated with said tuning fork and having its input circuit includesaid master time period device, said contacts and said fork, means forapplying negative potentials to the control electrode of said vacuumtube for predetermined conditions in the vibration of said tuning fork,a second vacuum tube having its control electrode connected with theoutput circuit of said first named vacuum tube and adapted to have-.thegrid potential thereon controlled in accordance with the strength ofcurrent flowing in the output circuit of said first vacuum tube,

means for controlling the rate of change of potential on the controlelectrode of each of said vacuum tubes, and means for controlling theperiod of vibration of said tuning fork in accordance with the strengthof current flowing in the output circuit of said second named vacuumtube for increasing or decreasing the frequency thereon in accordancewith variations between the coincidence of closure of said contacts dueto said tuning fork and said master time period device.

JOHN ARTHUR SMALE.

fork and adapted to be closed upon the 1n vigration of said tuning fork,a vacuum tube adapted to have a negative grid potential thereoncontrolled in accordance with the coincidence between the operation ofthe tuning fork and master time period device contacts, resistance meansfor gradually remov-

